Unable to install Dotnet: invalid character 'ï' looking for beginning of value

What version of Cloud Foundry and CF CLI are you using? (i.e. What is the output of running cf curl /v2/info && cf version? 6.32.0

What version of the buildpack you are using? 2.1.4

If you were attempting to accomplish a task, what was it you were attempting to do? Push application to CF

What did you expect to happen? Successful push

What was the actual behavior? The following container compilation failure:

-----> Dotnet-Core Buildpack version 2.1.4
-----> Supplying Dotnet Core
-----> Installing libunwind 1.2.1
       Download [https://buildpacks.cloudfoundry.org/dependencies/libunwind/libunwind-1.2.1-4bc9ce84.tar.gz]
       **ERROR** Unable to install Dotnet: invalid character 'ï' looking for beginning of value
Failed to compile droplet: Failed to run all supply scripts: exit status 15
Exit status 223

Steps to reproduce the error

I have to preface this by stating that I know exactly what is causing the error and how to get around it but I struggled to find helpful documentation on the cause so I wanted to file this issue in case it can be resolved on the Cloud Foundry end. If it cannot, hopefully this documentation will keep someone else from beating their head against the wall like I did.

In my case, I had installed the dotnet core 2.1.301 SDK but still have applications that are targeting the 2.0 framework. While it may not always be necessary to force these older applications to build/publish using an older SDK version, a "global.json" file can be used to force the desired SDK version to be used. With that in mind, do the following to reproduce this error:

Open Notepad and enter the following (NOTE: the actual version specified isn't really relevant):
```
{
"sdk": {
"version": "2.0.2"
}
}
```
Save the file to your project code base directory as global.json but SELECT UTF-8 AS THE DOCUMENT ENCODING VALUE instead of the default ANSI
Open a command shell, navigate to the project base directory and run dotnet --version to ensure that the SDK version specified in the global.json file is being properly detected and applied
```
C:\Code>dotnet --version
2.0.2
```
Prepare the application for pushing to Cloud Foundry by running dotnet publish (in my case I'm publishing to a sub-directory called "Deploy")
```
C:\Code>dotnet publish -c Production -o Deploy
```
Navigate to the publish/deploy location and attempt to push the build to Cloud Foundry
```
C:\Code\Deploy>cf push -f ../manifest-development.yml
```

NOTE: in my case, my .yml file is pretty straight forward


env:
INSTALL_NODE: false
NUGET_XMLDOC_MODE: skip
DOTNET_CLI_TELEMETRY_OPTOUT: 1

applications:

name: myAppName memory: 2048M instances: 1 buildpack: https://github.com/cloudfoundry/dotnet-core-buildpack.git domain: app.mydomain.com

env: ASPNETCORE_ENVIRONMENT: Development

* The error details specified in the section above should be the result of this push

**The reason the push fails is because by saving the global.json file as UTF-8, a byte order mark becomes part of the file content and for whatever reason, this causes the CF build to fail.**

### Steps to work around the error
The easy solution to the problem I specifically outlined above would be to simply open the global.json file again in Notepad and save it using ANSI encoding as this will inherently remove the byte order mark.  After that, you can publish and push again and the container should compile properly.

If your certain that your global.json file no longer has a byte order mark and your push continues to fail with the same error message, here's another thing you can do to locate other possible problem files:

* Open an instance of Powershell
* Navigate to the folder where you published your code
* Define the function and run the command seen below to inspect all the files in the directory (and sub-directories) for leading byte order marks:
```powershell
PS C:\Code\Deploy>
>> Function ContainsBOM
>> {
>>     return $input | where {
>>         $contents = new-object byte[] 3
>>         $stream = [System.IO.File]::OpenRead($_.FullName)
>>         $stream.Read($contents, 0, 3) | Out-Null
>>         $stream.Close()
>>         $contents[0] -eq 0xEF -and $contents[1] -eq 0xBB -and $contents[2] -eq 0xBF }
>> }
PS C:\Code\Deploy> get-childitem . "*.*" -recurse | where {!$_.PsIsContainer -and $_.Length -gt 2 } | ContainsBOM

    Directory: C:\Code\Deploy

Mode                LastWriteTime         Length Name
----                -------------         ------ ----
-a----        7/10/2018   2:06 PM           1697 appsettings.CloudFoundry.json
-a----        7/10/2018   9:37 AM           1697 appsettings.Development.json
-a----        7/10/2018   9:37 AM            766 appsettings.json
-a----        7/10/2018   9:37 AM           1893 appsettings.local.json
-a----        7/10/2018   9:37 AM           1621 appsettings.Production.json
-a----        7/10/2018   9:37 AM           1652 appsettings.Staging.json
-a----        7/10/2018   9:37 AM           1648 appsettings.Test.json
-a----        7/10/2018   9:37 AM           1795 appsettings.UAT.json
-a----        7/11/2018   9:02 AM             80 global.json
-a----        7/13/2018   9:29 AM            447 web.config

PS C:\Code\Deploy>

As you can see, all of the appsetting documents, the global and even the web.config have byte order marks in this case. I ONLY needed to ensure that the global.json wasn't using a byte order mark to get my push to succeed. None of the other files mattered when it came to successfully pushing.

At any rate, this is a pretty slick way to identify any other possible stragglers that might have an impact.

Please confirm where necessary:

[x] I have included a log output
[x] My log includes an error message
[x] I have included steps for reproduction
[x] I have included steps to work around the error

cloudfoundry / dotnet-core-buildpack

Unable to install Dotnet: invalid character 'ï' looking for beginning of value #191

Steps to reproduce the error